for People with a Passion for Period Property

The definitive guide to wood stripping and sanding

By Toby Newell
of Newell Polishers

Toby Newell is the owner of www.newellpolishers.com . He is an apprentice trained French polisher and wood restorer.

Introduction:

The art of wood finishing is a complex and fascinating subject. Because of the breadth of information on this important subject it would be impossible to cover all topics in depth so I will constrain myself to what appears to be one of the main areas of interest to many period property owners, the stripping of paint and varnish from wood. My aim is give an impartial, professional and comprehensive overview.

Be realistic:

It is important to be realistic in what you can accomplish confidently and safely and what is best left to a skilled craftsman. If you feel confident then you are likely to do a decent job, if however you have nagging doubts it is all too easy for a project to go "pear shaped" and cause more problems than it solves. Realising what you can safely accomplish is a skill in itself although sometimes the only way to find out is the hard way! Stripping and sanding are probably the most physically demanding and time consuming aspects of any wood restoration project, so plan your time carefully and as my Grandfather used to say, "Steady Eddie wins the race".

Stripping:

This section is divided into two parts:

  • Stripping floors, beams and other architectural items by hand.
  • Stripping floors by machine.

Stripping floors, beams and other architectural items by hand

There are two main ways of removing an applied finish from a wooden substrate.

  • Chemical means.
  • Mechanical means, including rubbing, scraping and sanding.

Heat can only really be used for the removal of paint and not varnish therefore is best reserved for exterior work where the wood is not left in its natural state.

In reality a combination of both mechanical and chemical methods are required when stripping wood because when you remove chemical stripper you will be using mechanical methods such as rubbing, scraping and digging. Remember sandpaper and wire wool are in themselves tools and in the wrong hands can do more damage than a power sander. It is also important to stress that you should not be put off using quality professional power tools per se, the reality is modern professional tools can sand far smoother than most humans and are surprisingly versatile. When used appropriately they can be of great assistance, although ultimately there is no substitute for the sensitivity and dexterity of the human hand, especially as old wood is very rarely flat.

Listed below are all the main modern day methods used to remove applied finishes from wood. Some are more appropriate than others. The advantages and disadvantages of each method are shown plus a wood finishing professional's perspective.

1. Chemical stripping

Benefits:

Gives the best possible result, quicker at removing finishes than sanding alone, can be the most gentle on the wood.

Drawbacks:

Chemical strippers are hazardous, care must be taken at all times and respirators may need to be worn.

Overview:

There are two basic forms of chemical stripper:
Caustic (alkaline, sodium or potassium hydroxide) normally thixotropic (viscous so they stick to vertical surfaces) paste and
Solvent based (usually methylene chloride based) non-caustic, may also be thixotropic.

You will need

Dustsheets; thick polyethylene or cotton plus newspaper for protection. Masking tape. Sharp cabinet scraper or modified decorators scraper (see SUMMARY) Stanley 1992 heavy-duty knife blades or equivalent. Coarse, number 5 (oak, ash, pine) or number 4 grade (fruit woods, maple, cherry etc) wire wool. Lint-free rags for washing, wiping and neutralising. Stripping chemical. Suitable container for decanting stripper into. Brush and/or spatula for applying stripper. Brass wire brushes and/or nylon brushes for cleaning. Newspaper/small cardboard box/bin bags for disposing of stripped finish safely. Gloves, goggles, overalls/apron dust mask/respirator as appropriate. Bucket of clean water. Methylated spirits/white spirits/acetic acid as appropriate for neutralising.

2. Solvent stripping

Benefits:

Will remove all finishes eventually, even modern ones. Very gentle, will not in itself damage the wood, the only stripper used in antique restoration for example. No discolouration. Nothing gets the wood as clean, even in the grain.

Drawbacks:

May prove more expensive to use than caustic strippers as you may use a greater volume of product. Can cause burns, gives off strong fumes, good ventilation required. Can be messy. Harder work to remove heavy paint build up than caustic strippers.

Method:

1. Always read the label and follow the safety instructions.

2. If you have poor ventilation or are stripping large areas consider a respirator with a filter for organic vapours (EN. 141)

3. Mask up adjoining areas and sheet up with thick polythene and/or cotton dustsheets. Keep a rag that has been dampened in white spirits handy to remove any spills or splatters.

4. Pour some stripper into a metal paint kettle or large glass jar (beware it will melt some plastic jars) apply to surface with a grass brush or an old paintbrush.

5. Leave for five minutes. The surface should start to bubble. You may need to apply another two, three or four coats, work it in with your brush, be generous, the more stripper you use the better.

6. Do not let the stripper dry out. When the finish starts to bubble and just before it starts to dry remove residue with a sharp cabinet scraper.

7. Apply another coat of stripper, let it soak in for five minutes then remove with number 4 or number 5 grade wire wool, you can work quite hard with the wool, always with the grain direction.

8. You should start to see the wood get completely clean; it should feel bare and not waxy.

9. You may need to repeat this process several times. Neutralise with methylated spirits (my choice) or white spirits (the manufacturers choice) by rubbing over with a wetted rag.

 

Professional view:

When specialist wood finishers talk about stripping, this is what they mean. For the professional 99% of the time this is the only way, it is hard work but gives a far superior finish and if done with care will not damage the wood.

3. Caustic strippers

Benefits:

Will remove most finishes. Especially good on thick paint build up. Less fumes than solvent based. Cheaper. Quicker.

Drawbacks:

The main ingredient, a very powerful alkaline chemical normally sodium or potassium hydroxide (as found in most oven cleaners) stains the wood by reacting with natural wood acids in the same way as fuming. It also attacks all living tissues slowly breaking down wood at a molecular level so can cause cracking and peeling of surface on damaged and old worm eaten timbers such as beams, especially if left in contact with the bare wood for extended periods. Beware, companies have to advertise such strippers as gentle on the wood or some people would not buy them, ask for a technical or COSHH data sheet (they have to supply them on demand by law) read the ingredients and make up your own mind. Can cause severe burns if not used properly.

Method:

1. Always read the label and follow the safety instructions.

2. Sheet up with dust sheets and polythene, mask adjoining areas and keep a damp cloth handy to remove splatters and drips.

3. Apply stripper as per manufacturers instructions, they are made in differing strengths but as a rule work best overnight on deep paint build ups, covering up with grease proof paper or polythene will stop it drying out and keep the stripper active for longer, applying more water can reactivate old stripper.

4. Remove with cabinet scraper, large chunks should peel away. May need to reapply.

5. Better method is to apply solvent stripper as advised above to remove last residue along with wire wool.

6. Remember to neutralise the remaining alkali with acetic acid (or white vinegar) really give it a good scrub.

7. After a few days a white powder may form, this salt is the reaction byproduct of neutralisation and can be removed by washing with clean water or by gentle sanding.

 

Professional view:

French polishers and wood finishers rarely, if ever, use this method. Any stripper in direct contact with the wood will cause staining and may actually damage the surface. Depending on the exposure time pine will go brown then dark brown; mahogany and oak will go dark brown to black. Even using powerful modern bleaches (which will further damage the wood) you may not be able to remove all of the staining and anyway the original patination will have been lost. I would therefore not recommend this stripper on wood that is to be left natural or where the original patination and colour is to be left intact, I would never use it on very old (over 200 years) worm damaged oak beams. On the other hand it is superior to solvent strippers at removing thick paint layers on relatively new and undamaged (e.g. 100 year old pine) artefacts where the wood is to be repainted or stained dark as the discolouration effect will not be so apparent. Also ideal for removing heavy paint build up on old floors before machine sanding as the aggressive floor machines should remove any staining.

What stripper:

All the solvent strippers are much the same. You may as well buy B&Q or Homebase's brand; it's cheaper than Nitromors. The only difference is Nitromors yellow which doesn't have a thickener added, it is excellent for mouldings, intricate work and less waxy but beware, it drips more than the thicker variety. Nitromors brown (varnish remover) is also slightly better at removing thick oil based coatings but there is not much in it. Cyclone, strypit and other brands that work just as well should be available at your local builders merchants in gallon containers at around half the price (pro rata) of smaller containers in the DIY stores.

Stripping floors, beams and other architectural items by Mechanical Means

1. Sand blasting

Benefits:

Very cheap, quick, very efficient at removing all finishes.

Drawbacks:

Very messy, unfortunately also very efficient at removing the underlying wood, destroying patination and damaging worm eaten areas. Can lead timber resembling driftwood.

Likely to require listed building planning consent if used to remove surface finishes in a listed property.

Method:

Abrasive particle bombardment accelerated by high air pressures and volumes. Contact sandblasting company, or hire equipment.

Professional view:

Personally I think there should be a law against its use because it completely destroys fragile timbers, patination, colour and form and has no place in wood finishing.

2. Sand/water/air combination blasting

Benefits:

More expensive, otherwise as above.

Drawbacks:

Less messy than sandblasting as well as gentler, but it still damages fragile and worm eaten areas leading to damaged patination.

Method:

Abrasive particle in high power water/air vortex. Same principal as sand blasting but much more efficient therefore requires lower volumes of air and abrasive thus reducing damage. Contact specialist company.

Professional view:

Fine for sound roof timbers in large barn conversions where surface finish is not critical and other methods not economically viable. Not recommended for fine finishes or where patination and/or historical markings are important. Will require further sanding afterwards to obtain smooth finish.

3. Power sanding (only)

Benefits:

Low skill level required to achieve reasonable finish, can be fairly clean

Drawbacks:

Can be very messy if no dust extraction available, can damage patination if not done with care, can take a lot longer than chemical stripping on heavily soiled areas due to abrasive clogging up.

Method:

1. Start off with coarse grit paper (as low as 36 grit on floors, 60 grit on everything else) and work your way through the grades up to the finer grits finishing with 120 for floors (finer may impair adhesion of floor finishes) or finer 240 for other woodwork.

2. Dust down, wipe and vacuum in between, a dust extractor prolongs the abrasive life and makes the job far less messy (you can connect your normal vacuum extension tube with masking tape but you may need to clean the filter regularly)

3. Finish by hand sanding with 240 or 320 grit paper on beams and doors.

4. For uneven floors with deep scratches or reclaimed wood with planing/sawing marks it may be quicker to use a sharp cabinet scraper to scrape out some of the damage before sanding.

5. Get the right tools for the job, belt sander for floors, a good orbital or random orbital, cheap machines are next to no use and can be slower and more tiring than by hand alone.

6. Use sanders in combination i.e. Belt, roughing orbital, random orbital getting a progressively finer finish. The idea is to clean the wood with the first pass using the coarsest grit, the subsequent passes are purely designed to remove the scratches from the previous pass until you cannot see or feel the scratches.

7. Finishing with 400 grit on a random orbital should feel like silk. (See also TOOLS AND MATERIALS)

You will need:

Sander (possibly extension cable) and appropriate abrasives. Sharp cabinet scraper, damp rags or tack rags for wiping down. Dusting brush. Dust sheets and masking tape for dust traps. Dust mask (essential) goggles, kneepads, earplugs or ear defenders (optional). Vacuum cleaner and/or dust extractor.

Professional view:

Power sanding alone is not the smartest method to remove applied finishes, it is okay for nearly bare, discoloured or rough timber or timber that has already had most of the finish removed by other means, is probably the slowest of all methods for stripping paint and other thick film finishes as the friction of the moving abrasive will just melt the finish and clog up repeatedly. Coupled with a dust extractor it is one of the cleanest of all methods.

Summary

Caustic strippers are good at removing heavy paint build-ups and for complex mouldings but may stain the wood and damage old friable timber surfaces. Best reserved for stripping pine doors etc that are to be stained dark or painted (it actually works best on plaster, stone and metal which are better able to withstand its caustic nature) Solvent strippers are more expensive and messy to use and worse on heavy paint but will not damage or stain the wood and generally give a cleaner, finer finish especially if going for the natural look. Along with scraping and sanding the only safe method to use on old oak and damaged beams. If in doubt, buy a limited quantity of different strippers and test them on small inconspicuous areas to see which you best prefer. A final sand either by hand or machine or by both will remove the final vestiges of residue. Use brass and heavy nylon brushes in corners and mouldings, stiff denture tooth brushes and heavy duty Stanley 1992 razor blades are handy for removing build up from awkward areas. Do not use shave hooks, they will dig into the wood. If you cannot get a quality cabinet scraper (which is really worth seeking out) then round off the corners of a decorators stripping knife with a file to avoid digs and scratches.

Machine sanding floors

This method is only applicable if your floor is relatively flat and in good condition, for example, Victorian pine or Edwardian oak parquet.

It is NOT suitable for heavily bowed or cupped floors, heavily worm eaten floors, those where you wish to retain more of the surface patination, houses/cottages with old and delicate plaster work below the floor being sanded (the vibration from the heavy machines can cause damage) If in doubt, always opt for the gentler hand finished method. (See above for details)

Machine Hire

Sanding floors is very hard work, as anyone who has done so will testify. Always hire the best machines and use the best abrasives as they make the job a lot easier. For areas over 50 square meters I would recommend the belt sander over the drum.

You will need to hire a large floor sander, either drum or belt and an edger. Remember, abrasives are expensive, hire companies make more money on their abrasives than on the machines themselves, budget at least the same amount for abrasives as the machine hire. If you are working upstairs remember you will need two people to carry the machines up safely, they are very heavy.

Drum sanders

  The ones you see on the TV, and in most hire shops. Look for the ones with clutches that allow you to raise and lower the drum whilst the sander is in motion.

Benefits:

Cheap to hire, easy to manoeuvre.

Drawbacks:

Slow, tiring, poor dust extraction, can leave "chatter" marks, hard to get really smooth finish.

Cost:

Expect to pay around 65 per day, 80 a weekend, 110 per week including an edger. Abrasives vary, but average around 2 to 3 a sheet.

 

Belt sanders

  The ones you don't see on the TV. The ones professionals use for sports halls, museums, galleries, hotels, shops etc.

Benefits:

Around twice as efficient, better dust extraction, very smooth finish possible, much less tiring to use, quicker job completion (around half the time)

Drawbacks:

More expensive, harder to manoeuvre in very small spaces, very heavy to lift upstairs.

Cost:

Around 100 per day. 135 a weekend. 250 per week including an edger. Abrasives around 12 per belt (but last 10 times longer)

 

Floor Abrasives

Aluminum oxide (red) cheap, blunts easily. Silicon Carbide (black) longer lasting, intermediate cost. Zirconia (blue) nearly as hard as diamond, hardly any need to change the sheets unless damaged or clogged, the most expensive, well worth it on larger floors for rough sanding.

You wil need:

Ear defenders or ear plugs. Dust mask or respirator. Goggles. Over suit (optional) Knee pads (optional) Machine sander and edger from hire shop with assorted grades of abrasive.

Hammer and nail punch. Pliers and /or tack remover. Screwdriver (for machine) Detail sander with abrasives. Cabinet scraper. Masking tape. Polythene dust sheets. Broom, vacuum cleaner, dustpan and brush.

Method:

1. Replace or repair damaged boards or strips. Remove superfluous nails, tacks and screws. Punch in the rest of the nails to a depth of at least 3mm to avoid damaging the abrasive and/or sander.

2. Tape polythene dustsheets across stairwells etc to contain dust to one floor level. Tape around door edges. Open windows.

3. Start with 24 grit for heavily soiled or uneven pine floors, 40 grit for normal pine floors and 40 or 50 grit for soft pine or parquet. Work through the grades not missing out more than one grade in between, finishing off with 100 or 120 grit. E.g. 24 then 36 then 50 then 80 then 100 then 120. Do the same with the edger. (also see TIPS below)

4. Sand in the direction of the boards (in the direction of the light with basket weave parquet) at an angle of 15 degrees to the horizontal to get a more aggressive cut, reverse the direction of cut with alternate grades (i.e.////// then \\\\\\) The aim is to remove all the scratches made by the previous grade.

5. Finish off perfectly straight with the finer grades (80 upwards). Sweep and vacuum in between grades to avoid contamination with the coarser grits.

6. Scrape out the corners and around radiators with a cabinet scraper finishing off with a detail sander.

7. Before staining or applying sealer run over the floor with a damp rag dipped in methylated spirits, this will act as a "tack" rag and remove the last vestiges of dust for a fine finish.

Tips:

1. Start moving gently before you lower the drum and lift it before you get to the end of the room. Never allow the sander to come to a rest when the drum is in contact with the floor.

2. Move quickly and lightly with the edging sander. NEVER use the edger close to radiator pipes, it will go through them in a second, stop a few inches away and finish off with a scraper and detail sander.

3. Remove all the old finish and discolouration with the coarsest grade, you will not be able to clean the floor with the lighter grades.

4. After the initial cleaning and leveling of the coarse paper the only purpose of the finer grades is to remove the previous scratches until finally you cannot see any.

5. Do not be tempted to skip grades or you will never get all the previous scratches out.

6. The exception is soft pine; to a certain extent it is ripped up rather than sanded smooth and you should start with no less than 40 (or 50 if you can) then 60 then 80 (you can even try leaving this one out) and 100, you may need to finish with a hand sander as any finer on the drum will still rip up the grain and may produce chatter marks.

Empty the dust bags regularly when less than one third full. Before undoing the bag from the machine, put a bin bag over the whole dust bag/collection tube and then undo the dust bag holding the bin bag closed as much as possible, this will greatly reduce the dust given off.

General Safety

Always read the label and follow the manufacturers safety advice. If you do not feel confident using a particular chemical or machine then leave it to someone who does. Dust nuisance masks are no good for solvents; you should wear a respirator with the appropriate filter (EN141 Organic gases and Vapours). Use a dust extractor if sanding lead paint residues, remove the bulk using other methods before sanding, wear a respirator for fine dust particles or a good dust mask like 3M's moldex range. Always have a first aid kit to hand. When using stripping chemicals it is advisable to have a bucket of clean water nearby incase of emergencies. Normal rubber gloves are no good, you need industrial rated rubber gloves, the really thick red ones with the cloth cuffs, MAPPA do a blue industrial glove that is excellent but very hard to find. Never tear coarse wire wool with bare hands, it will remove your fingers! Cut with scissors or tear with industrial gloves. Always dispose of waste products responsibly. Sawdust can be explosive, never burn it. Solvent stripper residue is flammable do not burn. Open solvent stripper cans away from your face as they can "spit" when warm. Keep away from heat. If in doubt, always stop and seek advice.

Tools and Machinery

Always buy or hire the best you can afford, cheap tools and materials are false economy. The difference between cheap DIY tools and materials and their trade counterparts is incomparable. Proper tools should last you a lifetime and will make your job easier, more rewarding and save you money. This is particularly true with sanders. Let's face it, no one likes sanding, the better the machine the less time you spend sanding, simple. The considerable loads placed on the motors of sanders means that cheap ones overheat, burn out quickly and are very underpowered; it is almost impossible to "stall" a professional sander. There are many websites selling trade tools and materials at discount prices to the general public, it is worth doing some research.

The average (median) price is what you should expect to pay for a decent professional tool from a dealer with discount. (DO NOT pay the RRP, trade dealers always heavily discount) If you are going to buy one sander go for the random orbital, five inch ones start at around 70 and are a million miles from the cheap orbital third sheets sold in the DIY stores. For a little more the Metabo SXE450 DUO has two settings, it will sand aggressively for removing finishes and smoothing then it can be set to the gentle mode for fine finishing, two sanders in one, highly recommended for the keen amateur, 150 well spent.

For sanders: Makita, Bosch (Blue professional range), Metabo and Hitachi (Green Professional range) are the best. Festo, Mafell and Fein are Rolls Royces but cost the same. DeWalt is a little overpriced. Hitachi has probably the best value professional sanders as they are not so well known but they are very well built and have excellent motors.

Random orbital sander:

Rotates eccentrically whist turning on its axis thus giving a total random pattern, not to be confused with cheaper plain orbital sanders, gives faster stock removal and finer finishes with no swirl marks, therefore excellent for preparing before staining. 5 inch 70 - 120 average 90, 6 inch 130 - 350 average 150. Makita, Bosch (Blue) Metabo, Festo, Mafell, Fein are the best.

Recommendation:

Metabo SXE450 DUO Super duty 6 inch Random orbital 150

Orbital sander:

Go for a half sheet industrial with a large orbit diameter for fast stock removal (sometimes called a "roughing" sander) don't bother with this as a finishing sander as a random orbital is infinitely better. 110 - 300 average 150. Bosch (blue) Makita, DeWalt and Hitachi (green) are good here.

Recommendation:

Makita 9046 Super duty half sheet orbital (Surprisingly now available in B&Q at a reasonable 150)

Delta sander:

Invaluable for getting into those nooks and crannies. 60 - 150 average 80. Bosch (Blue) and Metabo do them and they are twice as powerful as DIY versions, excellent for corners of floors.

Recommendation:

Metabo DSE300 Heavy duty delta sander 90

Belt sander:

If you have uneven floorboards or stairs to do go for the industrial 4-inch (100mm) type they are in a different league to the DIY sanders 150 - 350 average 230 and the belts are much more widely available. Makita or Hitachi are probably the best. DeWalt is expensive. Not for the feint hearted, very powerful and tricky to master, you have been warned.

Recommendation:

Makita 9403 4" (100mm) Super duty belt sander. The all new Daddy of belt sanders. 230

Dust extractor:

Once you buy one you will never know how you lived without one before. Connects directly to your tool and automatically starts when your power tool starts, can reduce dust by 98%. Can be used as a wet and dry vacuum as well. 160 - 400 average 220. There are loads to choose from, Numatic the makers of Henry do them, Draper does a cheap one, Hitachi and Fein are good.

Recommendation:

Fein QB35E portable dust extractor. 160 In a word, fantastic. (I have one) Filters down to 5 micron as standard, 1 micron and 0.3 micron (HEPA) filters available. Very quiet, can be used as a normal wet and dry vacuum cleaner.

Machine Abrasives:

Go for the best you can afford. These come in different weights of backing paper, the heavier the weight the better the paper, for really heavy work choose BW/RW grade. For finer grades after 100 grit it doesn't matter so much. Bosch Redwood is a good all-purpose power abrasive and is relatively easy to find. If you have a lot of work to do it is worth seeking out HERMES abrasives, as they are arguably one of the best.

Hand Abrasives:

As with sanders professional abrasives are in a different league and make all the difference. Luckily you can buy fairly decent paper at DIY stores these days, forget glass paper. Go for resin bonded Aluminum oxide at the DIY store. If you can find a specialist store, look out for 3M Tri-M-ite, Siafast lubrasil or EAC stearated silicon carbide paper, it's blue and white, self lubricating, lasts longer and gives a superior finish. 320 is probably the finest grade you will need for a silk like finish.

Disclaimer

Although we have taken great care to ensure that our information and advice is correct, we cannot accept any responsibility for any loss or damage incurred arising from the use of the information published on our web site. Before committing yourself to any expenditure, you are advised to check any details and costs beforehand.

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